WAVEGUIDE ARRAYS
A waveguide array can comprise a base portion having a metalized inner surface, an outer surface, and a clean end surface. The inner surface can include a plurality of waveguide channels that are metalized. The clean end surface can be prepared by breaking the base portion along a groove positioned on the outer surface prior to breaking, where the groove is oriented to intersect the waveguide channels. A metalized cover portion is attached to the inner surface of the base portion to close the waveguide channels.
As computer chip speeds on circuit boards increase to ever faster speeds, a communications bottleneck in inter-chip communication is becoming an increasing concern. One solution may be to use fiber optics or other waveguides to interconnect high speed computer chips. However, most circuit boards involve many layers and often involve small tolerances in their manufacture. Physically placing fiber optics connecting the fibers to the chips can be too inaccurate and time consuming to be widely adopted in circuit board manufacturing processes.
One partial solution is to use small, relatively finely detailed plastic parts for optically interconnecting various computer components, but their manufacture in accordance with appropriate tolerances can be challenging. In preparing small plastic parts in general, part of the manufacturing problem relates to the inherent effects of molding and other preparative processes, where plastic edges are not inherently crisp as plastic end faces often undergo shrinkage or other deformation. Removal of molded edges, however, creates other issues. For example, in attempting to use conventional machining, such as saw cutting or milling to create a clean edge on a small and finely detailed plastic part, burrs and/or undesirable breakages form at the edge of the plastic materials, exacerbating the problem. This can be particularly problematic in the area of optics.
Reference will now be made to the examples described and illustrated, and specific language will be used herein to describe the same. It will nevertheless be understood that no limitation of the scope of the technology is thereby intended. Additional features and advantages of the technology will be apparent from the detailed description which follows, taken in conjunction with the accompanying drawings, which together illustrate, by way of example, features of the technology.
It is noted that when discussing the waveguide array or the method of making the same, each of these discussions can be considered applicable to each of these examples, whether or not they are explicitly discussed in the context of that example. Thus, for example, in discussing details about the waveguide array per se, or the method, such discussion also refers to the other example, and vice versa.
With this in mind, it is understood that light beams or optical signals are frequently used to transmit digital data. For example, optical signals can be used to transmit data over large distances, between optoelectronic components on nearby circuit boards, between optoelectronic components on a single circuit board, or between circuit boards. For large scale interconnections between multiple optoelectronic components, an optical waveguide array can be used which can have a number of characteristics, including the ability to connect any or all of the inputs to any or all of the outputs with a minimal number of components. An optical waveguide array can also have a high coupling efficiency, modularity, high reliability, and low cost. Furthermore, optical waveguide arrays can be efficiently and inexpensively used for various other purposes, such as for point-to-point interconnects or broadcast bus applications in blade servers, computer servers, etc.
In accordance with this, the present disclosure is drawn to the preparation of waveguide arrays having clean end surfaces, which is useful for interconnection between other waveguides, electrical devices, or optical devices, as well as for providing a reduction in energy loss that can occur with end surfaces that are not as crisp or pristine as those prepared in accordance with examples of the present disclosure. Thus, a technique to singulate waveguide arrays without damaging the end surfaces during formation thereof, along with the possibility of preparing variable lengths of waveguide can be achieved in accordance with examples of the present disclosure.
More specifically, the present disclosure is drawn to a waveguide array and associated methods of making the waveguide array. The waveguide array can comprise a base portion having a metalized inner surface, an outer surface, and a clean end surface. The inner surface includes a plurality of waveguide channels that are metalized. The outer surface is typically flat, though this is not required. The clean end surface is prepared by breaking the base portion along a groove positioned on the outer surface. The groove in this example is oriented to intersect the waveguide channels. To complete the waveguide array, a metalized cover portion is attached to the inner surface of the base portion to close the waveguide channels. In one particular example, the waveguide array can include two clean end surfaces at opposing ends of the waveguide array. Further, in another example, the metalized cover portion can comprise a plastic substrate with a metalized surface, and the metalized surface is attached to the metalized inner surface of the base portion to close the waveguide channels. The clean end surface, formed from breaking the base portion along the groove, provide clean end surfaces that are perpendicular to the waveguide channels, or that are not necessarily perpendicular, but still intersect the waveguide channels.
Turning now specifically to the FIGS., examples of the present disclosure are shown, which are not necessarily to scale. In
Stated more generally, the present disclosure is drawn toward generating a partially cut groove or otherwise providing a partially penetrating groove 26 through the outer surface 24 of the base portion 10, followed by mechanically breaking the part at the partial cut or groove location. One reason for this approach is due to the fact that conventional machining leads to burrs, particles, or unacceptable damage to the channel and sidewalls of the waveguides. This technique creates pristine waveguide end surfaces 44 which substantially prevent aperturing or scattering of light beams entering and exiting the hollow waveguides of the array and minimizing optical energy propagation loss through the hollow waveguides. Because of this, by preparing more pristine end surfaces initially, elimination of the added step of “deburring” the waveguide channels after singulation by conventional machining is accomplished. Furthermore, though post-processing to “debur” the waveguide array is possible, it is not desirable; and furthermore, is not possible to repair broken sidewalls, which is another problem associated with machine cutting small plastic waveguide arrays using conventional machine cutting techniques.
The formation of the base portion 10 can be by any of a number of methods, including by molding, injection molding, extruding, embossing, roll-to-roll embossing, wet etching, or dry etching. The groove 26, on the other hand, can be prepared as part of the molding, embossing, or etching process in some examples. Alternatively, the groove can be prepared after the base portion is molded, extruded, embossed, or etched using a saw, hotwire, blade, end mill, diamond tip, or the like.
Typically, the groove 26 is prepared so that it is deep enough to generate a crisp, pristine break along base portion 10 (intersecting the channels), but not so deep that the groove enters the open channels 14 of the base portion, thereby causing damage to the channels. In some examples, a groove from 10% to 90% deep measured from the outer surface to the channels works well, though grooves outside of this range can also be effective (provided the open channels are not disrupted). In another example, the groove can be from 25% to 90% deep, and in still another example, the groove can be from 25% to 75% deep. The grooves are positioned along the outer surface 24 to intersect the channels, but they need not be perpendicular to the orientation of the channels. In one example, however, the groove or grooves are perpendicular to the channels. In another example, the groove or grooves are oriented to intersect the channels, but are not perpendicular to the channels. Furthermore, it is noted that there is often more than one groove on a base portion, such as for forming two pristine, clean breaks. Two breaks can be used to form a part with two clean end surfaces at opposing ends of the waveguide array. Furthermore, multiple parts can be prepared from a single base portion where multiple grooves are present to form multiple parts.
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Waveguide arrays, such as hollow metalized waveguides in particular, typically include a hollow air core surrounded by highly reflective metallic wall. The metallic wall is supported by a substrate of any suitable material, but often includes silicon, plastic sheets, or glass. A variety of patterning processes can be used to form hollow waveguide arrays in accordance with examples of the present disclosure, including wet and dry etching, extruding, molding, embossing, roll-to-roll embossing, and other suitable processes. For example, some forms of plastic molding are used to create trenches or open channels which can be metalized to form the waveguide array. According to a more specific example, the sidewalls and bottom of these trenches or open channels can be metalized using a sputtering process to provide a highly reflective surface at the wavelengths of interest. Silver can be sputter-coated into the trenches to provide the reflective coating. The silver can be overcoated with a passivation layer, such as aluminum nitride, which can protect the coating and prevent oxidization. An undercoat may also be provided to improve the adhesion of the silver layer to the substrate. A waveguide cap or cover portion can also be metalized on the substrate to cover the trenches and complete the waveguide array. Other metals may also be used in place of silver such as but not limited to gold, copper, or aluminum. As mentioned, typical dimensions of a hollow waveguide cross-section may be approximately 50-250 μm, for example. That being stated, the size and geometry of the waveguides can be altered according to the specific design.
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In accordance with examples of the present disclosure, multiple waveguide arrays and other devices can be optically connected using waveguide arrays of the present disclosure. For example, the waveguide arrays can optically couple backplanes, blades, and other devices in a server, or can be part of these devices. To illustrate one device, one can consider the backplane, which refers to a structure having multiple communication channels which can be accessed through a number of integrated sockets or other receptacles. For example, a backplane may contain a common bus to which a number of separate devices may connect. Backplane communication channels may include electrical wires, optical fibers or other waveguides (including the waveguide arrays of the present disclosure), or other channels. The backplane may contain optical to electrical transducers, signal processing electronics, various types of light sources. Where the term “optical backplane” is used, the backplane includes at least one channel which is configured to convey optical signals through the backplane.
While the forgoing examples are illustrative of the principles of the present technology in particular applications, it will be apparent to those of ordinary skill in the art that numerous modifications in form, usage and details of implementation can be made without the exercise of inventive faculty, and without departing from the principles and concepts of the technology. Accordingly, it is not intended that the technology be limited, except as by the claims set forth below.
Claims
1. A waveguide array, comprising:
- a base portion having a metalized inner surface, an outer surface, and a clean end surface, the inner surface including a plurality of waveguide channels that are metalized, the clean end surface prepared by breaking the base portion along a groove positioned on the outer surface prior to breaking, the groove being oriented to intersect the waveguide channels; and
- a metalized cover portion attached to the inner surface of the base portion to close the waveguide channels.
2. The waveguide array of claim 1, having two clean end surfaces at opposing ends of the waveguide array.
3. The waveguide array of claim 1, wherein the metalized cover portion comprises a plastic substrate with a metalized surface, and the metalized surface is attached to the metalized inner surface of the base portion to close the waveguide channels.
4. The waveguide array of claim 1, wherein the clean end surface is perpendicular to the waveguide channels.
5. The waveguide array of claim 1, wherein the clean end surface is not perpendicular to the waveguide channels.
6. The waveguide array of claim 1, wherein the waveguide channels have a cross-sectional dimension of about 50-250 μm.
7. A method of making a waveguide array, comprising:
- forming a base portion having an inner surface and an outer surface, the inner surface including a plurality of open channels, the outer surface including a groove oriented to intersect the open channels, but which is not deep enough to disrupt the open channels;
- breaking the base portion along the groove to form a clean end surface on the base portion; and
- attaching a cover portion to the inner surface of the base portion to form an array of closed channels, wherein the array of closed channels are metalized.
8. The method of claim 7, wherein the array of closed channels are metalized by applying a metal coating to the inner surface prior to breaking, and applying a metal coating to the cover portion prior to attaching the cover portion to the inner surface.
9. The method of claim 7, wherein the array of closed channels are metalized by applying a metal coating to the inner surface after breaking, and applying a metal coating to the cover portion prior to attaching the cover portion to the inner surface.
10. The method of claim 7, wherein the step of forming the base portion is by molding, injection molding, extruding, embossing, roll-to-roll embossing, wet etching, or dry etching.
11. The method of claim 7, wherein the groove is formed using a saw, hotwire, blade, end mill, or diamond tip.
12. The method of claim 7, wherein the groove is formed as part of a molding, embossing, or etching process.
13. The method of claim 7, wherein the groove is from 10% to 90% deep measured from the outer surface to the open channels.
14. The method of claim 7, wherein the groove is perpendicular to the channels.
15. The method of claim 7, wherein there are multiple grooves on one base portion, and the multiple grooves undergo breaking to form multiple clean end surfaces.
Type: Application
Filed: Jan 27, 2011
Publication Date: Aug 2, 2012
Patent Grant number: 8503848
Inventors: Sagi Varghese Mathai (Palo Alto, CA), Paul Kessler Rosenberg (Sunnyvale, CA), Michael Renne Ty Tan (Menlo Park, CA)
Application Number: 13/015,546
International Classification: G02B 6/10 (20060101); B23P 17/00 (20060101);